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4.1.3 RS-422 CONNECTION USING TERMINAL BLOCKS
If your RS-422 application requires you to connect two pairs of
bare wires to the Model 222N, you will need to open the case to access
the terminal blocks. The following instructions will tell you how to open
the case, connect the bare wires to the terminal blocks, and fasten the
strain relief collar in place so that the wires won't pull loose.
1. Open the unit by gently inserting a screwdriver between the
DB-25 connector and the lip of the plastic case (see below). You don't
have to worry about breaking the plastic, but be careful not to bend the
D-sub connector.
Once the unit has been opened, you will be able to see the
terminal blocks located at the rear of the PC board.
2. Strip the outer insulation from the twisted pairs about one inch
from the end.
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3. Strip back the insulation on each of the 2 twisted pair wires
about .25".
4. Connect
one pair
of wires to XMT+ and XMT- (transmit positive
and negative) on the terminal block, making careful note of which color
is positive, and which color is negative.
5. Connect the
other pair
of wires to RCV+ and RCV- (receive
positive and negative) on the terminal block, again making careful note
of which color is positive, and which color is negative.
Ultimately, you will want to construct a two pair cross over cable that
makes a connection with the RS-422 device as shown below:
Model
222N RS-422 Device
XMT+.............................RCV+
XMT-..............................RCV-
RCV+.............................XMT+
RCV-..............................XMT-
6. If there is a shield around the telephone cable, it may be
connected to "G" on the terminal block. To avoid ground loops, we
recommend connecting the shield at one end only. A ground wire is
not
necessary
for proper operation of the Model 222N.
7. When you finish connecting the wires to the terminal block, the
assembly should resemble the diagram below:
+RCV- G -XMT+
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